Unlock Trilby Highlands:
Buy it from the Deku in the cave in Trilby Highlands.
Unlock Hyrule Town:
First shrink, then enter the shop at mamas cafe. Grow, take the bottle then talk to the guy. Then go to lake hylia and feed the dog in his house.
Unlock Your House:
Fuse kinsyones with master smith. Then go to Eastern Hills and pick up the bottle in the chest.
Unlock Eastern Hills:
Finish the Goron sidequest to unlock Eastern Hills.
Open Locked Hyrule House:
Collect original 130 figurines.
Unlock Great Spin Attack Upgrade no.1:
Fuse kinstones with Swordsman Trainer in Mt. Crenel.
Unlock Great Spin Attack Upgrade no.2:
Fuse kinstones with Swordsman Trainer in Lake Hylia.
Get the Swordsman newsletter:
Fuse kinstones with the postman in Hyrule Town.
Get the Carlov Medal:
Collect all 136 figurines.
Get the Golden Tingle Statue:
First complete all kinfusions then talk to Tingle.
Unlock Sound Test:
First get all 130 Original figurines then talk to the guy outside sitting at the table.
Getting the Magical Boomerang:
Another optional item to collect would be the upgrade to the old Boomerang from past Zeldas. As you know, you can buy the regular version for 300 Rupees in the town shop, but if you get this one first, you save yourself that money. Anyway, after you get the Mole Mitts, you'll find 4 Tingles scattered throughout Hyrule. If you fuse Kinstones with them, you'll find that caves will open up in the 4-tree formation in North Hyrule Field. Go into each of those caves and hit a switch to partially open the middle area. Do this with all 4 and a ladder will appear in the middle; go down and open the chest to get the Magical Boomerang. The locations of those Tingles are as follows (you may need certain items to reach them):
Ankle: Lon Lon Ranch
David Jr.: Lake Hylia
Knuckle: Trilby Highlands
Tingle: South Hyrule Field
(supplied by: SpinkByUs)