Free version has 50 puzzles. If you want play 75/100 puzzle version, you have to buy full version.
Here is full version Linex X

The Lines X Free store page really needs to be updated. Its description still shows "75 brain-teasing Numberlink puzzles". It also shows "Full version - Lines X", "Infinite fun - Lines Infinite", and "Get both with 25% discount - Lines Bundle", but the bundle doesn't exist (clicking the link brings you to the Steam home page).

The Lines X store page and Lines Infinite store page also show that same "Get both with 25% discount - Lines Bundle" text/link, and the link doesn't work on those pages, either.

Hey guys,
thanks for mentioning. 75->50 updated.
Regarding bundles - it's not available in countries where its price is below $0.49. That's general Steam rule.

Originally posted by Konstructors - Nestor Yavorskyy:

Hey guys,
thanks for mentioning. 75->50 updated.
Regarding bundles - it's not available in countries where its price is below $0.49. That's general Steam rule.

I'm not sure what the issue was with the bundle. At the time of my post (December 30), both Lines X and Lines Infinite were on sale for 0.49 USD each, so the bundle should have been 0.74 USD (0.98 USD minus 25% bundle discount). At any rate, the link is working again on all three product pages (Lines X Free, Lines X, and Lines Infinite), so whatever the issue was has been resolved. I just mentioned it in that post in case it was a dead link or a discontinued bundle.