I connected an usb device to my sinotec st-26kc42h and switched it to usb mode without an remote now its stuck there how can i reset

You can try a power reset, remove the mains plug overnight.

Or you buy a new remote. ALL televisions need a remote. You need the model number.

https://www.google.com/search?q=Sinotec+55inch+UHD+Digital+replacement+remote

https://www.fixya.com/support/r29872378-universal_remotes_no_facsimile_remote

..

I doubt you can. Only basic functions can be done from the set. You need the Source or Input button.

Google

make model replacement remote.

Run through Source or Input on the remote.

You have a 1 in 10 chance. How lucky do you feel?

https://www.eliztech.com/remotes/codelists/sinotec-tv-codes

Just google

make model replacement remote

and buy a facsimile copy of the original.

Here is one and it doesn't mention the other model

Sinotec Replacement TV Remote RC-J36 - Soundtech Online

https://soundtech.co.za > Brands > Telefunken

Description. Remote-TV - Sinotec compatible with TV models. ST-24KC70FN. YKF-Z18A01. SKU: RC-J36 Categories: Remotes, Telefunken, TVs and Remotes ...

you posted to computer help for TV? why not post to TV?
best , always is RTM read the manual no 2 TV work exactly the same. (nor did tell what you expect of that USB port?)
the post lacks the real and full Sinotec model number on that sticker on the rear, so getting the exact manual proves impossible.
so ill read the first one to you.
quote Page 21 in 1st manual I find on this brand,
TVs are no like Computers in the way USB is more predictable.
TVs love to fail, for wrong for formats. (fat32, or ntfs or?)
My guess's (wild) is a movie file is on a USB memory stick.?
I can put any movie.mkv on my stick plug it in and use it.
it shows up on TV as and INPUT device.

Notes about using USB

= Before using this function, make sure that you select the correct source (USB) and insert a USB storage device on

the TV to view compatible photo, movie and text on the TV screen or play compatible music through the TV.

= If the connected USB HDD does not have an external power source, it may not be detected. Be sure to connect the

external power source.

= To avoid losing the data on your USB device or damaging your USB device, it is recommended that you back up your USB

device data.

= The USB multi media playing menu may vary in different situations.

= If you want to pull out the USB device, please exit USB mode first.

= For instructions on using your USB device, refer to the owner's manual for your USB device.

= Never remove the USB device or turn off the TV while using the USB device. Doing so may result in loss of data and/or

damage to the USB device and/or TV.
= Certain types of USB devices may not be compatible with this TV.
page 21 also shows hitting USB button on remote (lost that?)o
and see photos on a USB or a movie. Photos , movie or text it tells.

here is my wild guess on the model.
https://www.manualslib.com/manual/918457/Sinotec-St-29me70h1.html?page=23#manual


the TV has multimedis player inside, this works for USB.
page 26 covers what movie FILE formats work.
format the usb stick as Fat32 is one safe first guess and try.
good luck with using USB. (the manuals on TV are very very limited on (what it needs to work right)on this TOPIC.
one poster back 2014 this brand
tells. supports fat16/32,and NTFS. and JPG,PMP and PNG photos. and what page 26 tells you,.

Most of those brand TV's should have function buttons on the side of the unit behind the screen.

Look on the right and left sides behind the screen and you should see them.

I just googled Sinotec and found an O/M which shows it, so you can Google your TV's model # to confirm.

This one shows it on page 5.

https://www.manualslib.com/manual/918457/Sinotec-St-29me70h1.html?page=7#manual

St-39kc70 sinotec

Set-up (Programming) procedure is too much to type in here, and is not practical and it will differ brand-to-brand remote controls. If you wish to get more; check the sites linked here. The site has set-up code list & set-up procedure to many popular brand remote controls. The site has general set-up codes to check with TVs and other devices are given, in the order of the 'device's brand name list' in alphabetical order. Set-up code list to many brand remote controls also is given. Pull up older posts. Search the sites by type in the brand name to your device in its search box at the top right part of the display window. It will help you to find the document easily.
http://electro-medical.blogspot.com/

Without its remote control, you can't select its inputs.
If you wish to buy its original remote control, contact the authorized service centre, or authorized dealer to your device brand. They can either give you a genuine remote control to your device, or can direct you, from where can you purchase a suitable one.
If you wish to get more; check the site linked here. It has set-up code list & set-up procedure to many popular brand remote controls. Pull up older posts.
http://electrohelponline.blogspot.com/
http://remotesearch.blogspot.com/

You do not need a remote control. I used my smart phone with IR. Down load tv remote apps and wala its sorted.dont buy universal remote it did not work for me could not find the Sinotec that i have so wasted R400.00