After STP is complete, can I continue with SIP in that particular fund?

Yes, you can continue with SIP in the same fund after the STP is complete. However note that some funds may stop subscriptions suddenly due to various reasons (e.g.: fund has too much ‘AUM’ or fund has undergone a crisis, like some debt funds did with the IL&FS crisis).

Go for an online platform that can support both SIP, STP, SWP in direct plan mutual funds. Beware of ‘free platforms’ that my advertise or push funds not in your best interest.