You want to send this over and over? If not, it belongs in setup().
Tests how many bytes of data there are to read.
inchar = cell.read();
Reads ONE of them.
The Answer1 should be "OK"
No, it should be 'O' or 'K', assuming that the TC35 responded to the request. You'll have to look at the documentation, and confirm that +CREG=1 is a valid AT command, and that it causes the phone to generate a response.
Once you know whether the phone has registered, why would you want to send the same command again?