Google Music – How to Update Metadata for Multiple Files

Not yet.

You can visit google.com/takeout to see the services which Google currently lets you export your data from.

You can also visit the "Data Liberation" website to see Google projects where data can partially be exported.

However, neither of those list Google Music at all, and a random comment says it doesn't work yet, so the evidence is that no, you can't.
_{(Not being a US resident, Google Music isn't available to me, so I can't say for certain.)}

No, there is no limit, but Albums may end up split or joined based on information in the Track Info and Album Info.

Here is an example of multiple albums merged into one: If you note, there are 52 tracks in the album and there are also a number of duplicate track numbers, as well as multiple artists.

This can be further explained by looking at the Album Info: Here we see some key elements empty:

• Artist
• Album Artist
• Tracks

Though these are not required they can help group the tracks. Which, if we look at a few of the Track Info panels:

We see the missing info cause a common pattern linking separate albums into one. Adding an Album Artists can quickly change my issue, but since you are looking to merge albums/collections removing elements from the track info (that would help ensure proper grouping of tracks) should give you the results you are looking for.

But I'd recommend using the "Playlist" feature, that Google provides, to get better results for groups and minimize future confusions should you decide to share your tracks.