I have two questions.

First question:
§ 1.52 requires that each sheet include a bottom margin of at least 2.0 cm and that the page number be centrally located above or preferably below, the text.
Can the page number be located within the bottom margin?
In other words, is the bottom margin measured from the page number ?

Second question:
§ 1.52 requires that each sheet include a left side margin of at least 2.5 cm, but does not require a line number (e.g., every five lines).
Do patent practitioners usually number the lines ?
Can the line number be located within the left side margin?

P.S.
PCT rule says as follows:
Page numbers must not be placed in the margins (PCT Rule 11.7(b)). Line numbers should appear in the right half of the left margin (PCT Rule 11.8(b

The "line number (e.g., every five lines)" is completely different from the paragraph numbering used when submitting a specification, which is what you appear to be referring to in the CFRs.

The paragraph numbering when submitting a specification, as discussed in 37 CFR 1.52 (b) (6) is OPTIONAL. The format should be a four-digit number enclosed in square brackets before every paragraph (with many exceptions such as headers, titles, formulas, tables, sequence data, and of course once you get into the claims section you don't use these numberings, you just number the individual claims).

Example:
Quote
AUTOMATIC RICE COOKER WITH TEMPERATURE SENSOR
[0001] The present invention relates to rice cookers, and more specifically to rice cookers that also serve as steamers.
SUMMARY OF THE PRIOR ART
[0002] Automatic rice cookers are common household appliances. They typically use a temperature sensor to gauge when the water has been fully absorbed or evaporated. A sudden temperature rise above 100 deg.C indicates that the rice is done.
[0003] However, this prior art system has significant drawbacks.
[0004] ...

Let me know if you have any problems...maybe i can help

Thanks. That answers my question. There was just a little bit of ambiguity.