Homosexual acts are illegal under UAE law and can incur a jail term and fines. If you see Arab men walking hand in hand, it's a sign of friendship and not an indication of sexual orientation.
Public displays of affection between LGBT+ partners are taboo.
Many LGBTIQ-related websites, including Grindr and other dating apps, are blocked and not officially accessible from inside the UAE.
Sex outside marriage is against the law. Sharing a room is likely to be construed as companionable or cost-cutting, but being discreet about your true relationship is advisable.
A useful read is Gay Travels in the Muslim World by Michael Luongo.
LGBT Rights UAE (www.facebook.com/LGBTRightsUAE) is a non-governmental organisation that strives to raise awareness about the issues facing the community.