No
To date, no horse has ever appeared on a British One Pound coin. There has been a unicorn as part of the Royal Arms on the 1983, 1993, 1998 and 2003 One Pound coins.
There is a one pound coin and a two pound coin but not a three pound coin.
The 1983 One Pound coin was the year of first issue for the British One Pound coin which replaced the One Pound note. The British One Pound coin is legal tender anywhere in the United Kingdom and some of its dependencies.
The British One Pound coin is round.
That would be a coin of the Irish pound, which has since been replaced by the euro.
Such a coin does not exist. The British One Pound coin was first issued in 1983.
The coin you describe is a Gibraltar One Pound coin commemorating the discovery of a Neanderthal skull in 1848. They were the standard issue One Pound coin in Gibraltar for a number of years.
There was no 1811 British Sovereign or One Pound coin minted.
There was no 1977 British One Pound coin minted. The first general circulation One Pound coins was minted in 1983.
The British decimal One Pound (nickel brass) coin was first issued in 1983. A gold One Pound coin was issued from about 1489 until 1604.
The British One Pound coin, as distinct from the "Sovereign" coin, was introduced in 1983 to replace the Bank of England One Pound note. See the link below.
The One Pound coin replaced the One Pound note in the British currency in 1983. Pound coins include the One Pound and Two Pound coins, and the Five Pound coin which is issued as a commemorative but is still legal tender.