If you're not trying to be the best Catherine player in the world and just want the achievements, do yourself a huge favor and play PAIRS
Even if you don't have a friend to play with, PAIRS by yourself with 2 controllers is so much more easier then playing solo.
1. Less steps.
PAIRS Alter: 106 steps
PAIRS Menhir: 130something... I forgot to take note.
PAIRS Obelisk: 154 steps
PAIRS Axismundi: 168 steps
2. Simpler Blocks
The game compensates the fact that you're playing with two people and gives easier blocks to deal with (i.e less cracked blocks, wider areas to work with)
3. Less/simpler strategy specific
While you can do a pairs Inazuma, you don't need it for PAIRS. The basic push/pulls, tornados, spider crawls, and push into the background to generate new blocks to work with is all you need.
Just to give an idea how much easier it is with PAIRS, I never made it past 130 solo on Alter after multiple hours spent, but I completed it first try in pairs.
Well... time for me to celebrate my 1k in Catherine.