Good day everyone,

Currently I'm making a thesis to see how political stability affect economic growth. I've already read Roodman and Sebastian Stata Conference Power Point. I just want to make sure how to interpret this clue from the paper into my stata code.

All explanatory variables were treated as endogenous. Their two period lagged values
were used as instruments in the first-difference equations and their once lagged first differences
were used in the levels equation
Lets say i have this regression where Y is dependent variable (gdp per capita [constant US$]), x1,x2,and so on is independent variable that affect Y and treated as endogenous as the clue said, without any strictly exogenous variable. And i have 1 external variable let say Z1.

Code:
xtabond2 Y l.Y X1 X2 X3 X4 X5 X6 X7 i.year, ///
gmm(l.Y X1,lag(2 2) eq(level)) ivstyle(Z1 i.year, eq(level)) ///
twostep robust small
And here the result:
Code:
Dynamic panel-data estimation, two-step system GMM
------------------------------------------------------------------------------
Group variable: cn_dum                          Number of obs      =       244
Time variable : year                            Number of groups   =        28
Number of instruments = 23                      Obs per group: min =         5
F(16, 27)     = 771184.44                                      avg =      8.71
Prob > F      =     0.000                                      max =         9
------------------------------------------------------------------------------
             |              Corrected
           Y |      Coef.   Std. Err.      t    P>|t|     [95% Conf. Interval]
-------------+----------------------------------------------------------------
           Y |
         L1. |   .9404939   .0293483    32.05   0.000     .8802762    1.000712
             |
          X1 |   .2708204   .2023615     1.34   0.192    -.1443912     .686032
          X2 |   .0406301   .0325983     1.25   0.223     -.026256    .1075162
          X3 |   .0280611   .0497435     0.56   0.577    -.0740041    .1301264
          X4 |   .0033058   .0012955     2.55   0.017     .0006477    .0059639
          X5 |   .0007148   .0012643     0.57   0.576    -.0018794     .003309
          X6 |   .0972347       .102     0.95   0.349    -.1120519    .3065213
          X7 |  -.0008346   .0007057    -1.18   0.247    -.0022826    .0006134
             |
        year |
       2010  |   .0231396   .0131364     1.76   0.089    -.0038141    .0500934
       2011  |   .0140576   .0176286     0.80   0.432    -.0221133    .0502285
       2012  |   .0203068   .0194618     1.04   0.306    -.0196255     .060239
       2013  |   .0235703   .0198685     1.19   0.246    -.0171964     .064337
       2014  |   .0053819   .0084616     0.64   0.530    -.0119798    .0227437
       2015  |   .0081878    .006552     1.25   0.222    -.0052558    .0216314
       2017  |  -.0037178   .0054981    -0.68   0.505    -.0149989    .0075633
       2018  |  -.0040531   .0083803    -0.48   0.633     -.021248    .0131418
             |
       _cons |  -.6609487   .6290191    -1.05   0.303    -1.951589    .6296918
------------------------------------------------------------------------------
Instruments for levels equation
  Standard
    Z1 2009b.year 2010.year 2011.year 2012.year 2013.year 2014.year 2015.year
    2016.year 2017.year 2018.year
    _cons
  GMM-type (missing=0, separate instruments for each period unless collapsed)
    DL2.(L.Y X5)
------------------------------------------------------------------------------
Arellano-Bond test for AR(1) in first differences: z =  -2.15  Pr > z =  0.032
Arellano-Bond test for AR(2) in first differences: z =   0.60  Pr > z =  0.548
------------------------------------------------------------------------------
Sargan test of overid. restrictions: chi2(6)    =   6.18  Prob > chi2 =  0.403
  (Not robust, but not weakened by many instruments.)
Hansen test of overid. restrictions: chi2(6)    =   3.19  Prob > chi2 =  0.784
  (Robust, but weakened by many instruments.)
Back to my question, when im trying to interpret this
Their two period lagged values were used as instruments in the first-difference equations
What come in my mind is
gmm(l.Y X5,lag(2 2) eq(level))
**) Even all explanatory are treated to be an endogenous, i'm not using all of it since it will raise my sargan/hansen test.

And for this statement
Their once lagged first differences were used in the levels equation
I'm not making any code since my code didn't use a first difference form on this code
xtabond2 Y l.Y X1 X2 X3 X4 X5 X6 X7 i.year
So, is there something wrong with my code? Sorry i'm not good in english, i hope you understand what i mean.

Have a nice day