How to get rid of the two zeros on far right in hp12c?

Press g [END].

Use the square root function. It's the g-shifted function of the 1/x key (second key from the left on the second row).

Press f ALG to switch to the Algebraic mode.

ALG is the shifted function of the EEX key.

To switch the radix mark, turn the calculator off, press and hold the decimal point key, press the ON key, then release both keys.

It's right above the double-height ENTER key in the center of the keyboard.

Press g [END] to set payments at the end of a period instead of at the beginning.

It indicates that the calculator is set for compound interest on the odd period instead of simple interest. To toggle this setting press STO EEX.

It could be some dirt or grit in the keyboard, which a blast or two of compressed air might clear out. It could be a worn dome on the inside of the keyboard.
If you want to have it repaired, there's FixThatCalc, though they're currently not taking new orders. There also have been several threads on opening and cleaning Voyager series keyboards at the Museum of HP Calculators. Here's one article on opening a Voyager.

To switch the radix point between the US and European modes, turn the calculator off, press and hold the decimal point key, press and release the ON key, then release the decimal point key.

Right click, coose the last option, and choose the format you want it to show as.


Like:
Currency $1.99
Custom (13 decimal places) 1.987454328720