Not at the moment (afaik). You can walk infinite into one direction (which @Saint_X did) which caused a lot of migration problems in the past (eg. on Civini).
No, there is a minimum size that must be adhered. If there won’t be one, the world would not be “spherical” eighter because the worlds are only “mathematical” round and not in real (visual).
Please stop asking this question again and again. As long as there is no C++ build there can’t be a PS4 release. And even if the C++ build (beta) is out, it won’t be a PS4 beta. Unfortunatly you need to wait till (or close to) Version 1.0 for a PS4 Version (or beta).