Where I can get the complete biography/hagiography of Ramanujacharya, which contains all the details of his life and deeds, right from his birth, till his passing away? Fantastic accounts are also fine.
There isn't a single comprehensive work outlining the complete biography of Sri Ramanuja. These are some of the more well known somewhat older works that describe his life:
- Yatiraja Vaibhavam of Vaduga Nambi, a student of Sri Ramanuja is a biographical poem in 114 Sanskrit verses. You can read an English translation here. This is the oldest known biography.
- The 6000-padi Guruparampara Prabhavam of Pinbazagiya Perumal Jiyar is a Manipravala Biography of the Srivaishnava Guru Parampara. The Tengalai tradition subscribes to this version of events. It is supposed to be written in the 14th century but there is a doubt as to the period of the author as some portions of later texts appear verbatim in it. It is the earliest extant (in print) elaborate discussion of Ramanuja's life. You can can read it here: Tamil script
- The 3000-padi Guruparampara Prabhavam of the 3rd Brahmatantra Svatantra Svami is a Manipravala Biography of the Srivaishnava Guru Parampara. The Vadagalai tradition subscribes to this version of events. It was written in the late 15th/ early 16th centuries. The author says that the first Brahmatantra Svatantra Svami wrote a biography in 12000 verses that was abridged by the second Svami in 6000 verses that was further abridged to the present form. You can read it here: Tamil script, Telugu script
- Prapannamritam of Anantacharya. Sanskrit version here. It has been observed to be almost a literal translation of the 6000-padi GPP. It is considered to be written in the second half of the 17th century.
- Divyasuri Caritam of Garudavahana Pandita. This is a Sanskrit poem biography of the Sri Vaishnava Guru Parampara from the Azvars through Ramanuja. It is unclear if the author is the same Garudavahana Pandita who was a contemporary of Ramanuja or not. There is a verse in it that suggests that it was written when Ramanuja was still alive but modern historians opine that it is written in the 15th or 16th centuries. You can read the Sanskrit text and Hindi translation here.
- Koil Olugu - A Tamil chronicle of the Srirangam Temple shines some light on Ramnuja's influence. It was fully translated to English. You can read an abridged English translation here.
- Yatiraja Saptati of Vedanta Desika is a poem praising Ramanuja in Sanskrit. It shines some light on certain aspects of Ramanuja's life. You can read and English translation here -
- Periya Tirumudi Adaivu - supposed to be written by Kandadai Nayan of the 15th century is clearly a later work as it details the life of people known to have lived a century after the author died.
- Ramanujarya Divya Charithai - Don't know much about it
Besides these, there are several English biographies of Ramanuja that sample bits and pieces from these above texts.
Life of Sri Ramanuja by Swami Ramakrishnananda published by Ramakrishna Mission is a very ddetailed, authentic and beautiful book: https://www.amazon.in/Life-Sri-Ramanuja-Swami-Ramakrishnananda-ebook/dp/B01N6P5BNH
The most authentic biography of Ramanujacharaya is Ārāyirappaṭi Guruparamparāprabhāvaṃ. This is only available in some Sri Vaishnava mathams headed by Jeeyars only. It is not available in English.
Alkondaville Govindacharya authored many books related to Sri Vaishnava tradition. He also wrote a biography in his own words which contain a detailed life of Ramanujacharya with the name The Life of Ramanujacharya: The Exponent of the Visishtadvaita Philosophy. This book is available on many platforms for scholars. I am giving link to the book available on archive.org.