No, "firsts" is not grammatically correct. It should be "first."
The plural of the noun "first" (an inaugural or premier accomplishment) is firsts.E.g. "The Soviet Union was responsible for many firsts in space exploration."
Firsts - 2013 First I Do 2-10 was released on: USA: 1 March 2014
No.
First submarine
Firsts - 2013 First STD 2-4 was released on: USA: 1 March 2014
Firsts - 2013 First Goodbye 1-4 was released on: USA: 31 October 2013
Firsts - 2013 First Proposal 2-9 was released on: USA: 1 March 2014
Firsts - 2013 First Therapy Session 1-5 was released on: USA: 31 October 2013
Firsts - 2013 First Sick Day 1-10 was released on: USA: 31 October 2013
Firsts - 2013 First Game Night 1-9 was released on: USA: 31 October 2013
Firsts - 2013 First Double Date 2-7 was released on: USA: 1 March 2014