What is the difference between unicode and ascii?

Unicode is a superset of ASCII, and the numbers 0–128 have the same meaning in ASCII as they have in Unicode.ASCII has 128 code points, 0 through 127. It can fit in a single 8-bit byte, the values 128 through 255 tended to be used for other characters.

What Bobby said is correct. ASCII (American Standard Code for Information Interchange) was originally a 7-bit code for American computers. Later it was extended to 8-bit and called Extended ASCII. As computers spread to countries that didn't use English, UTF (Universal Type Format) was standardized to handle all language characters. UTF-8 and Extended ASCII are virtually identical. UTF-16 is worldwide.

You can press the arrow key.

You should either take it to a phone repair shop or try and fix it yourself, look at wiki hows on fixing your phone from water damage.