the above question
Do you mean while you are a student seeking your first bachelor degree or applying after you already have one bachelor degree?
If you already have a bachelor’s degree, then typically you have to follow the transfer student admission process, see https://admissions.illinois.edu/Apply/second-bachelors and https://admissions.illinois.edu/Apply/Transfer/open-closed. Admission as a transfer is quite difficult to CS – currently you would need a 3.87 college GPA to be considered, only a small percentage of transfer applicants are usually admitted, and you would face the college’s favoring transfers who are seeking entry into junior year over others.
If you mean you want to seek a second degree in CS while a student at Illinois seeking a first degree in another UIUC college, then you would face the specific second degree rules at Illinois, including that you would need to request entry into the college/department for the second degree starting in junior year, you would need an exisitng GPA of about 3.8, and you would face an evaluation that factors in the probability that you can complete both degrees in 5 years while automatically adding 30 hours to the total hours you need to complete your first degree.
What are open and close at https://admissions.illinois.edu/Apply/Transfer/open-closed ?
The page you are looking at gives you determinations made in relation to transfer applicants for entry into Spring 2019 or Fall 2019 semesters. Examples: business college will accept no transfers for the Supply Chain Management program: the engineering college will accept none for bioengineering; transfer into CS is closed for anyone without at least 50 college credit hours (at time of actual transfer, not necessarily time of applying) and realistically CS typically does not take transfers until into junior year. Second bachelor degree applicants are not accepted at all by the Applied Health Sciences, Business, Education, and Media colleges, and that includes both someome who already has a degree and current students from another UIUC college, such as someone in engineering, who would like a second degree from one of those colleges.
Do i understand correctly that requirements for second bachelor in CS from UIUC are high school and college transcripts, toefl score and standardized tests?
If following the transfer admission process, those are required with two possible exceptions: (a) SAT/ACT scores are required only if you have completed less than 30 college semester hours when applying: (b) Toefl, if you need to de,onstrate English proficiency, is not the only test that can be used to do so, but is a common choice; UIUC also accepts the IETLS. Note also that if applying after having already completed thirty college hours, your high school transcript is mainly used to prove you graduated form high school and your high school grades are not part of the evaluation for admission.