Before signing up here, make sure you meet all the eligibility criteria:

• You need to be based in one of the eligible countries: Austria, Belgium, Belarus, Bulgaria, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Israel, Italy, Latvia, Lithuania, Netherlands, Norway, Poland, Portugal, Romania, Russia, Slovakia, Slovenia, Spain, Sweden, Turkey, Ukraine, and the United Kingdom (including Northern Ireland).
• Your game was published on or after 3 March 2020. It must be publicly available on Google Play (at least in the UK) by 1 July 2021. 
• You can have a maximum of 50 full time employees.

And other requirements in the legal Terms and Conditions. 

• Once submissions close, all eligible entries will be reviewed and up to top 20 finalists will be chosen by the Google Play team based on the level of innovation, fun, and technical & production quality.
• The 20 finalists will submit pitch videos and join a Q&A event with the jury. 
• All 20 finalists will get the opportunity to showcase their games at an online event open to the public, where the Top 10 finalists and 3 winners will be announced.