regarding his period quite a few questions go unanswered
the main point is was he before the other three or after.( sambanthar, navukarasar and sundarar) the main reason for the dispute is as far as i know the three dont mention him and he doesnt mention them either
the three have not sung about thiruperunthurai( auvudaiyar kovil) or uthirakosamanagai- two of manikarvasakars favourite temples
chidambaram was his addiction. half his songs are about thillai. and in one shiva himself acted as a stenographer and wrote down the lyrics as manickavasagar recited them. he merged with nataraja here .
but he is suppoosed to have conducted debates with buddhists and made a dumb sinhala princess speak here. that should give us a clue. the buddhists were living in one corner of tamilnade ever since the jains gained dominance. even the jains were vanquished in the 8th century by sambanthar. so manickavasakar must have lived in the era when budhdhists were dominating.
also he seems to have been a pm of a powerful pandya king whose writ ran strong till auvudaiyar kovil ( possiblu kodumbalur nadu) when were the pandyas so strong? it was that time that he possibly lived. venketesh
We know that Thirunavukkuarasar was a contemprory of Mahendra Pallava and since Thriugjanasambandar was contemporous with Appar, his times are also fixed.
Was the Pandya king- husband of Mangayarkarasi "Koon Pandiyan" same as Arikesari Parankusa Maravarma/Nellai Nidra Nedumara of Pandyas.
Sundarar was a contemporary of Cheraman Perumal, since it is current theory that Cheraman was the last of the Perumal kings of Kerala, his empire he dissolved before going off to kailash according to Saivities and to Mecca according to Muslims, that has been kept as the begining of the Kollam era.
It is Manickavasagar who is still proving elusive. Scholar are still interpreting allusions to him in Appar's work (Nari-Pari Story) and also the unidentified adiyaars in Sundarar's Thiruthondar thogai(?) the forerunner to NambiandarNambi's Thiruthondar Thiruvandhaathi and then Chekkizhar's Periya Puranam. But the other side of scholastic argument is reference to Sambandar and Sundarar in Thiruvasgam.
I am not that knowledgable in that area. SO gave wht input I could