Informally, you're likely to hear 1, 2, 5 & 6.
A bit more formally though, you'd likely hear 2 and 6. Pounds are a countable noun, so we use the plural.
However, pounds and other units of currency can also be used as a measurement. The "five-dollar milkshake" in "Pulp Fiction" isn't a grammatical error. Likewise, we would say "a two pound-forty milkshake" rather than a "two pounds-forty milkshake".
Is the answer the same if "pound/pounds/penny/pence" is replaced with "dollar/dollars/cent/cents"?
The plural of the English name for some currencies is the same as the singular, (e.g. yuan, yen, won, baht), so the equivalent examples have nothing to tell them apart.
The Italian lira had lire as the plural even in English, so the same rules applied, but with an unusual plural. It was replaced by the euro in 2002.
The euro is the strangest case. By law, all Eurozone states must use euro as the singular of the currency, but may spell it according to the rules of the language or languages including other scripts (hence ევრო, евро, ευρώ, eòra and various other forms in different languages that are all pronounced "euro"). The word is also declined according to the rules of a given language.
For some reason that is not entirely clear, euro was used as the plural form in English-language EU legislation. This was likewise followed by Irish law (Ireland and Malta are both Eurozone countries with English as an official language). It was then in turn followed by news articles and information campaigns in the run-up to the currency's adoption.
This was objected to on linguistic grounds by some, including this one-man campaign.
It was conceded that normal English pluralisation by adding an -s can be used. It's also common just because that's how English words are most often pluralised. But it remains in the form euro in much official literature.
The net result of all this, is that the euro-equivalents of forms 2 & 6 in your question could have the word spelled euro or euros, and there remain some with strong opinions one way or the other.