I'm surprise to see statistics in Google Analytics page for one of the Android app and noticed the following strange informations
Apple iPhone in Top Device Models

Strange OS names entry in OS Versions :
- Macintosh Intel 10.10
- Linux x86_64
- Windows 7
- (not set) (not set)



Note:
I have answered the the current possible solution, but that doesn't make corrections to the available old data sets please let me know any ways to correct the old data sets and get out of the cons mentioned in my answer!


Bots and referral spam are two different things, the answer you posted will only help with bots. I am going to refer to the article about removing referral spam here
Normally we say there are three types of junk visits:
Issue Number 1
I suspect data being inserted directly into the Analytics account directly though the measurement protocol. I say this because I have several old Google analytics accounts that are showing hits, the websites for these accounts no longer exist and haven't existed in years. I also have an old application account like yours that no longer has any data sent to it that shows data daily. The only way for data to be inserted into them is if someone is doing it directly, the hits are coming from known referral spam sites (the big list). There has been a lot of talk on the net lately on how to deal with the first two problems. Google has not come with any solution as of my writing this. The article gives a few very good ways of dealing with it. here
Issue Number 2:
This will be hard to detect, they are actually thing your site. A filter on the known bad crawlers helps.
Issue Number 3
The answer you posted is correct but will only help with this: Bot and Spider Filtering. Its also kind of old.