What do the red light with abell shape which is lit up mean on my 18 year old tricity bendix freezer mean

Green light usally means that the freezer is in good working condition. Red light means the door is slightly open and wasn't shut properly. Sometimes the seal on the door has gotten old or twisted.

Green light means that freezer is connected to the mains/electric

Red means that your freezer has not reached minimum working freezing temperature, this is not good news, something may be wrong with your freezer, get it checked by a competent person.
yellow light means that you have switched the fast freeze button on. This yellow switch allows the freezer to run continuously so that the frozen food you brought home from shopping can freeze up quicker. You must not leave this light on for more than 3 hours. It will cause you to waste a lot of electric and will place a lot of stress on the working component in the fridge.

Red light lit on freezer means that is not reaches operating temperature.

Most often the old freezer has three indicator lights.
- Green light : that it is brought to a power source and turned on - Red light : means that the temperature is above -18 degrees
- orange light : pressing the so-called SUPER-switch which means that the compressor is running continuously. The SUPER-button switch on a few hours before you begin deep-freeze foods. Freezing time depending on foods quantity (kg). With old freezer must be careful to turn off the switch S (orange light) when the red light goes out or when foods are frozen, otherwise after a few days may burn out the compressor. You should be following the instructions from user manual.
In new freezer managed by the electronics, this function has a predetermined maximum duration, in order to protect the compressor, and can have different marketing names like "shopping".....

Dado

I have the same issue, the green light on the bottom is not lit. Looked in manual and do not see anything about that. Freezer is working otherwise, everything frozen like it should be.

two reds and green are the auto max freeze on indecators the reds go off one at a time when unit drops to safe temp mode.also means unit needs defrosting manually when too much ice is present.

depends on what condition it is in in most cases yes as long as the doors and body are in good shape meaning doors not loose and hanging or holes or dings in the body to allow air and moisture to get in

Is this just a "Power-on" light to let you know it's plugged in and has power? This is probably just a "neon" (although the actual gas inside is hydrogen for the green color) bulb and sometimes they will do the flickering thing literally forever. In a way it's a good thing as it makes you look at it. If it really concerns you, or if it is actually a warning that something is going wrong (it should say in the manual, you DO have the manual don't you?) have it fixed under the warranty.

this means that temp is below -18 deg Celsius,and probably compressor is not good,or gas is leaked.

My recommendation is to get rid of this 18 year old freezer as it is costing u a fortune to keep it plugged in. Then ask yourself if you really need an additional freezer at all?? If you do, consider purchasing a new small one that is really energy efficient. You will be way money ahead I assure u.

Check the vents of your fridge side if present, if no air then may be your blower not working or some ice formation that blocks the air(try defrosting). Check also your vents for obstruction or overloaded with stocks.