Consensual sex between two adult person is not illegal in India, but the lady partner should not be the wife of some other person.
As far as age is concerned, it is not an issue here. Messages and intimate photos are ample proof of having intimate relationship. In case, the opponent if filed a case/complaint against you before the competent court pf jurisdiction, your presence is required. As far as working VISA is concerned it depends upon the nature of complaint.
Substantial proof for promise of marriage are electronic messages, video, letters etc.
Rape can not be termed as 'false petition'. Rape is an offence under Sec 376 of IPC where police has all powers/authority such as arrest/investigation or as provided to them in cognizable and non-bailable offence. The competent court of law has jurisdiction to decide whether it is a false case of rape or otherwise.