A) The mode of the text in question is spoken, it has been lifted from a speech or conference Tony Blair gave outside Downing Street on the 4th September 1997, regarding education for children of the UK.
B) I would suggest that this example of language has a rather high degree of formality due to its purpose; it is an official conference regarding a rather important matter and therefore Tony Blair will have made an active effort to keep the language to a certain and relatively high degree of formality. The language however is not overcomplicated and I think this is done so that various people from different backgrounds across the UK can understand what changes may take place in their education system, which is relative to almost any UK resident.
C) From the text it can be inferred that Tony Blair has quite a wide array of spoken lexis and he makes use of this throughout. He uses words of varying formality to create a professional yet accessible approach to what is being discussed. In terms of grammar, Blair is generally accurate but it is hard to determine what pauses are intentional, for effect or any other reason due to the format of the text, spoken. For example, the commas seem to be in the right places throughout and I can only assume these are placed where he would pause in his speaking. There are some interesting examples in the text however that make it quite clear that this format of text is rather different to written or electronic. For example, Blair starts one of his sentences with “And I suppose…” The word ‘And’ is a strange word to see at the start of a sentence, and it is a lot less likely to be found in written language as more thought would be put into the structure and grammar of the text. This may be due to the fact that spoken language is rarely recorded and is generally not permanent, leading to a lack of care and precision in terms of grammar.