I am interested in doing:

(1) MLM with a continuous dependent and independent variable,
(2) Assessing interaction by time,
(3) Assessing interaction of above by group

I wanted to make sure that I am proceeding correctly, both programmatically and interpretation-wise.

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To start, I have the following syntax to evaluate (1) and (2) above:

xi: xtmixed sym sat time sat_time || ID: time, variance covar(un) mle

where sym (my continuous dependent variable) = disease symptom level (higher numbers means more symptoms),
sat (my continuous independent variable) = satisfaction with healthcare (Likert scale of 0 strongly disagree to 4 strongly agree),
time = time variable (year 1-year 5), and
sat_time = interaction between satisfaction with healthcare and time
ID = identification number of participant

If this is correct, and if there is significant interaction by time (i.e., sat_time p<0.05), how would I interpret the results?

I want to know how satisfaction with healthcare relates to disease symptom level, and whether or not this varies by time. If it varies by time (i.e., sat_time p<0.05), what would the coefficient tell us? Is this the unit increase in disease symptom level over time per unit increase of satisfaction level with healthcare?

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To assess (3), I added to the previous syntax in the following:

xi: xtmixed sym sat time grp sat_time sat_grp time_grp sat_time_grp || ID: time, variance covar(un) mle

where grp = intervention group (1 vs. 0),
sat_time = interaction between satisfaction and time
sat_grp = interaction between satisfaction and group
time_grp = interaction between time and group
sat_time_grp = interaction among satisfaction, time and group

If there is significant interaction by group (i.e., sat_time_grp p<0.05), how would I determine the direction of association for each group and whether each 'main effect' is significant for each group? Would this be the following syntax:

lincom sat_time /*group=0*/
lincom sat_time + sat_time_grp + /*group=1*/

I assume the interpretation remains the same as above but tailored to each group where there is significant 'main effect', with a negative coefficient interpreted as a unit decrease in symptom level over time per unit increase in satisfaction level with healthcare. Your assistance and confirmation would be much appreciated.