Can SQL server 2016 SP2 restore to SQL server 2008 R2?

OriginalGriff is right, however there are tools to convert databases that might be able to do this. Most of these tools are paid, but the free version of Power Architect might be able to do it: https://www.slant.co/topics/10827/viewpoints/7/~relational-database-design-and-modelling-tools~sql-power-architect[^]
Also see: https://www.slant.co/topics/3250/~relational-database-migration-tools[^]

Another option would be to write your own conversion utility, here is an example that converts SQL Server to PostgreSQL. Only thing you need to do is change PostgreSQL to SQL Server 2008 :)
Convert SQL Server Database to PostgreSQL[^]
Btw, we dropped SQL Server in favor of PostgreSQL a long time ago, and never regretted it !