Issey Miyake Bao Bao bags

Hi, does anyone knows the operating hours for the Marunouchi stores near Tokyo station?

If you are talking about the one located inside "Kitte" building (shopping/office complex), the shops in that building are open from 11:00 - 21:00 on weekdays & Saturdays, and until 20:00 on Sundays & national holidays.
The one in Yusen Building (also in Marunouchi area) is open 11:00 - 20:00.

We had an early arrival & expect to reach Tokyo Station around 8am. Does all mall around Tokyo station open at 11am?

In Japan, department stores and malls open at.. 10 am at earlist, some places at 11 am. For example, around Tokyo Station, Daimaru Department Store opens at 10:00. In-station food shops (including sweets shops) are... for example GranSta (inside Tokyo station) open from 8:00. Yaesu Chikagai (underground shopping mall on the Yaesu side) are open from 10:00, except for breakfast locations that open at 8:00.

But the two buildings you've mentioned earlier open their fashion boutiques at the times mentioned. (There are offices in these buildings, so convenience stores and some coffee shops would be open earlier, though.)

Any recommendation for breakfast around the area, prefer those with wifi available for us to spent the 2-3 hours. AnyStarbucks around?

There is one each in Marunouchi Building (Maru biru) and Shin Marunouchi Building (Shin Maru Biru) on the basement floor.