Is There Limitation of Variables in Form Submission?

Yes,

You may need to submit over 1000 variable data from Web Form. In this case, the number of variables are default limited by 1000 variables in PHP

This is default configuration in php.ini file.

If you need more, please set the max_input_vars=5000 in php.ini

Reference: http://php.net/manual/en/info.configuration.php#ini.max-input-vars