Question : MySQL can handle how many concurrent transactions?

how many concurrent transactions MySQL can handle? Is there a limit?
how many records in a table he can handle at maximum?

Answer : MySQL can handle how many concurrent transactions?

For records in a table, you're constrained by disk space, and the number of bits used in your OS.  See here for a brief description:

http://jeremy.zawodny.com/blog/archives/000796.html

I've not found a limit on concurrent transactions, but I believe it will be limited by available memory.  Just a guess, though...