Questions About P, NP, languages
1.) Every context free language is decidable. CFL are not unrecognizable. Refer 1

2.) P is countably infinite because P is the class of decision problem that can be solved on a deterministic turing machine in polynomial time. Every turing machine can be thought of as a finite string over some finite alphabets but all possible set of turing machines are countable infinite hence P is also countably infinite.

3.) NP complete languages are recognizable. A NP Complete languages can be found by modifying the halting problem which is just another form of halting problem(NP-Complete). Halting problems are undecidable but recognizable hence all NP-Complete problems are recognizable. Refer 2 fro details.