The analyses of a text #2

The narrator recalls his adolescence.
He visited his old friend Traddles' place for the first time, and there met his old friend Mr. Micawber as Traddles' land lord who had been a debtor quite a while.
And he invited Taddles and the Micawbers to his apartment.

'But punch, my dear Copperfield,' said Mr. Micawber, tasting it, 'like time and tide, waits for no man. Ah! it is at the present moment in high flavour. My love, will you give me your opinion?'
Mrs. Micawber pronounced it excellent.
'Then I will drink,' said Mr. Micawber, 'if my friend Copperfield will permit me to take that social liberty, to the days when my friend Copperfield and myself were younger, and fought our way in the world side by side. I may say, of myself and Copperfield, in words we have sung together before now, that
We twa hae run about the braes
And pu'd the gowans' fine
- in a figurative point of view - on several occasions. I am not exactly aware,' said Mr. Micawber, with the old roll in his voice, and the old indescribable air of saying something genteel, 'what gowans may be, but I have no doubt that Copperfield and myself would frequently have taken a pull at them, if it had been feasible.'
[David Copperfield by Charles Dickens]
1. I'd like to know what "social liberty" means.
2. I'd like to know what "of myself and Copperfield" means.
3. And I'd like to know what the difference between "take a pull," and "take a pull at" is.
Thank you in advance for your help.