Accessing the full set of Unicode characters?

In another thread (re: Foreign Language Character), accessing Unicode characters in XPP was described as using "Shift + F2 and then typing [the 3 digits]..." In the cited example, the lstrok character was accessed via the 3 digits 1 4 2.

Does this work if the Unicode includes letters (e.g., O_acute - Unicode number U+00D3) ref. HTML-code Ó Entity Ó?

Does this work if the Unicode includes 4 characters (e.g., Right_Heavy_Arrow - Unicode number U+27A7) ref. HTML-code ➧ no Entity?

What's the best way to access the full set of Unicode glyphs that may be available in a particular font? Does the XPP FAST need any special configuration for those special characters that are within the font - that is, characters that are NOT in a symbol or dingbat font? Does this require setting up special XPP Keyboards or Macros?

Note: The text is coming in as XML created with XMetal.

Thanks in advance for any replies.