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This article will help with growing and caring for these ferns: https://www.gardeningknowhow.com/ornamental/foliage/maidenhair-fern/maidenhair-fern-care.htm

Yeah, if the leaves have all turned brown, you've got a problem. In my experience, maidenhair fern is a rather touchy plant to grow indoors, because it is very finicky, and responds to conditions beyond its liking by dying rather emphatically. If you left it outdoors, it may have got too much light, it probably went too dry - they HATE getting dry - then it may have got too wet. If you take it indoors where you won't forget it, give it medium light (light is good if there's enough for you to read comfortably,) and keep it moist but not soaked, it may regrow. You can cut off the brown fronds, they won't come back. Hate to say it, but probably the whole plant is a goner. If you're interested in houseplants, the plants in this article are great in the home also: https://www.gardeningknowhow.com/houseplants/hpgen/best-office-plants-good-plants-for-the-office-environment.htm

Yes, you can divide the plants to give them more growing space. Repot as needed, whenever the ferns outgrow their container. See this article for more:

https://www.gardeningknowhow.com/houseplants/hpgen/should-you-repot-your-plant-happy-root-bound-house-plants.htm

The best potting mix for maidenhair fern is one that contains a high proportion of peat moss mixed with organic matter.

https://www.gardeningknowhow.com/ornamental/foliage/maidenhair-fern/maidenhair-fern-care.htm

There are several varieties of Maidenhair Ferns.

The American Maidenhair Fern, Five Finger Maidenhair Fern and Northern Maidenhair are hardy in zones 3-8.

https://www.gardeningknowhow.com/ornamental/foliage/maidenhair-fern/maidenhair-fern-care.htm

Many times those lush looking plants you see in the stores have just arrived from the growers, so they are quite happy.

Lack of humidity in the home is a big reason for difficulty in growing Maidenhair Ferns or any ferns.
Taking the ideal growing location and then trying to reproduce those growing conditions indoors can be a challenge but can be done.

Trays of pebbles and water can help with humidity and daily misting.

Maidenhair Ferns are often called "the Diva's of ferns' so you are not alone in having trouble growing this beautiful fern!

http://www.uvm.edu/pss/ppp/articles/fernsin.html

Browning leaf tips in ferns can also be due to low humidity. Increasing the humidity in the room should help. There are some more possibilities, like excessive salts or fertilizers in the soil, that you could check into:

https://www.gardeningknowhow.com/plant-problems/environmental/what-causes-brown-edges-on-leaves-of-plant.htm